Key frame detection and synchronization

ABSTRACT

Mechanisms are provided for allowing a streaming server to efficiently provide frames associated with a media stream to a client device. A streaming server receives multiple media streams and determines which frames in the multiple media streams are key frames. When a connection request is received from a client device, a key frame is selected and provided to the client device. A client device receiving a key frame does not have to drop any predictive frames prior to playing a media stream.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority of pending U.S. patent applicationSer. No. 13/973,178 filed Aug. 22, 2013, which claims priority to U.S.patent application Ser. No. 11/626,340, now U.S. Pat. No. 8,542,705,filed Jul. 23, 2007 which are incorporated herein by reference in theirentirety.

DESCRIPTION OF RELATED ART

The present disclosure relates to media streams. In one example, thepresent invention relates to methods and apparatus for efficientlyproviding a media stream to a client device.

Various devices have the capability of playing media streams receivedfrom a streaming server. One example of a media stream is an MovingPicture Experts Group (MPEG) video stream. Media streams such as MPEGvideo streams often encode media data as a sequence of frames andprovide the sequence of frames to a client device. Some frames are keyframes that provide substantially all of the data needed to display animage. An MPEG I-frame is one example of a key frame. Other frames arepredictive frames that provide information about differences between thepredictive frame and a reference key frame.

Predictive frames such as MPEG B-frames and MPEG P-frames are smallerand more bandwidth efficient than key frames. However, predictive framesrely on key frames for information and can not be accurately displayedwithout information from key frames. A streaming server often has anumber of media streams that it receives and maintains in its buffers.In some examples, a streaming server maintains one buffer per channel.When a client device connects to a streaming server, the streamingserver provides a selected media stream to the client device. The clientdevice can then play the media stream using a decoding mechanism.

However, mechanisms for efficiently providing media streams to clientdevices are limited. In many instances, media streams are provided in amanner that introduces notable delay. Consequently, the techniques ofthe present invention provide mechanisms for improving the ability of astreaming server to efficiently provide media streams to client devices.

OVERVIEW OF THE INVENTION

Mechanisms are provided for allowing a streaming server to efficientlyprovide frames associated with a media stream to a client device. Astreaming server receives multiple media streams and identifies keyframes in the media streams. When a connection request is received froma client device, a key frame is selected and provided to the clientdevice. A client device receiving a key frame does not have to drop orinaccurately display any predictive frames prior to playing the mediastream.

These and other features and advantages of the present invention will bepresented in more detail in the following specification of the inventionand the accompanying figures, which illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, whichillustrate particular embodiments of the present invention.

FIG. 1 is a diagrammatic representation showing a sequence of videostream frames.

FIG. 2 is a diagrammatic representation showing another sequence ofvideo stream frames.

FIG. 3 is a diagrammatic representation showing one example of a networkthat can use the techniques of the present invention.

FIG. 4 is a diagrammatic representation showing one example of astreaming server.

FIG. 5 is a flow process diagram showing processing at a streamingserver.

FIG. 6 is a flow process diagram showing processing at a client device.

DESCRIPTION OF PARTICULAR EMBODIMENTS

Reference will now be made in detail to some specific examples of theinvention including the best modes contemplated by the inventors forcarrying out the invention. Examples of these specific embodiments areillustrated in the accompanying drawings. While the invention isdescribed in conjunction with these specific embodiments, it will beunderstood that it is not intended to limit the invention to thedescribed embodiments. On the contrary, it is intended to coveralternatives, modifications, and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claims.

For example, the techniques of the present invention will be describedin the context of particular networks and particular devices. However,it should be noted that the techniques of the present invention can beapplied to a variety of different networks and a variety of differentdevices. In the following description, numerous specific details are setforth in order to provide a thorough understanding of the presentinvention. The present invention may be practiced without some or all ofthese specific details. In other instances, well known processoperations have not been described in detail in order not tounnecessarily obscure the present invention.

Various techniques and mechanisms of the present invention willsometimes be described in singular form for clarity. However, it shouldbe noted that some embodiments include multiple iterations of atechnique or multiple instantiations of a mechanism unless notedotherwise. For example, a processor is used in a variety of contexts.However, it will be appreciated that multiple processors can also beused while remaining within the scope of the present invention unlessotherwise noted. Furthermore, the techniques and mechanisms of thepresent invention will sometimes describe two entities as beingconnected. It should be noted that a connection between two entitiesdoes not necessarily mean a direct, unimpeded connection, as a varietyof other entities may reside between the two entities. For example, aprocessor may be connected to memory, but it will be appreciated that avariety of bridges and controllers may reside between the processor andmemory. Consequently, a connection does not necessarily mean a direct,unimpeded connection unless otherwise noted.

Streaming servers receive media streams such as audio and video streamsfrom associated encoders and content providers and send the mediastreams to individual devices. In order to conserve network resources,media streams are typically encoded in order to allow efficienttransmission.

One mechanism for encoding media streams such as video streams involvesthe use of key frames and predictive frames. A key frame holdssubstantially all of the data needed to display a video frame. Apredictive frame, however, holds only change information or deltainformation between itself and a reference key frame. Consequently,predictive frames are typically much smaller than key frames. Ingeneral, any frame that can be displayed substantially on its own isreferred to herein as a key frame. Any frame that relies on informationfrom a reference key frame is referred to herein as a predictive frame.In many instances, many predictive frames are transmitted for every keyframe transmitted. Moving Picture Experts Group (MPEG) provides someexamples of encoding systems using key frames and predictive frames.MPEG and its various incarnations use I-frames as key frames andB-frames and P-frames as predictive frames.

A streaming server includes a buffer to hold media streams received fromupstream sources. In some examples, a streaming server includes a firstin first out (FIFO) buffer per channel of video received. When a clientdevice requests a particular media stream from the streaming server, thestreaming server begins to provide the media stream, typically byproviding the oldest frame still in the buffer. A client device mayrequest a media stream when a user is a changing a channel, launching anapplication, or performing some other action that initiates a requestfor a particular media stream or channel. Due to the relativeinfrequency of key frames in a video stream, the client device will mostlikely begin receiving predictive frames. Predictive frames rely oninformation from a reference key frame in order to provide a clearpicture. The client device can then either begin displaying a distortedpicture using predictive frame information or can simply drop thepredictive frames. In either case, the user experience is poor, becausethe client device can not display an undistorted picture until a keyframe is received. Depending on the encoding scheme, a substantialnumber of predictive frames may be received before any key frame isreceived.

Consequently, when a user initially requests a particular program orchanges a channel, there is notable delay before the user can see anaccurate picture. A variety of limitations contribute to the delay. Thetechniques of the present invention recognize that the transmission ofunusable predictive frames upon a connection request is one factor thatcontributes to the delay.

Some available solutions rely on increasing the transmission rate to aclient device when a client device connection request is received. Inthis manner, predictive frames and key frames are transmitted morerapidly to a client device when a client requests a media stream and akey frame is more likely to arrive sooner. However, there is still delayin transmitting a key frame. Furthermore, not all networks support thistype of transmission burst and even ones that do may not want toencourage this type of possibly disruptive activity. For example, manyusers may request to receive a channel at the beginning of a live event.Having a large amount of burst activity may be disruptive to networkoperation.

In many conventional implementations, streaming servers are designed toprovide large amounts of data from a variety of sources to a variety ofclient devices in as efficient a manner as possible. Consequently,streaming servers often perform little processing on media streams, asprocessing can significantly slow down operation. However, thetechniques and mechanisms recognize that is it beneficial to providemore intelligence in a streaming server by adding some additionalprocessing. By using a smart, key frame sensitive buffer in thestreaming server, an initial key frame can be provided to the user whena client device requests a connection. Bandwidth is better utilized,wait time is decreased, and user experience is improved.

According to various embodiments, a streaming server identifies keyframes in media streams maintained in one or more buffers. When aconnection request is received from a client device, a key frame isprovided to the client device even if the key frame is not the firstavailable frame. That is, a key frame is provided even if one or morepredictive frames are available before the key frame. This allows aclient device to receive a frame that it can display without distortion.Subsequent predictive frames can then reference the key frame.Connection requests such as channel changes or initial channel requestsare handled efficiently. Although there may still be delay intransmission and delay in buffering and decoding at a client device,delay because of the receipt of unusable predictive frames is decreasedas a streaming server will initially provide a usable key frame to aclient device.

FIG. 1 is a diagrammatic representation showing one example of asequence of frames. According to various embodiments, a sequence offrames such as a sequence of video frames is received at a streamingserver. In some embodiments, the sequence of video frames is associatedwith a particular channel and a buffer is assigned to each channel.Other sequences of video frames may be held in other buffers assigned toother channels. In other examples, buffers or portions of buffers aremaintained for separate video streams and separate channels. Inparticular embodiments, key frame 101 is received early along time axis141. One example of a key frame 101 is an I frame that includessubstantially all of the data needed for a client device to display aframe of video. Key frame 101 is followed by predictive frames 103, 105,107, 109, 111, 113, 115, and 117.

According to various embodiments, a sequence of different frames types,beginning with a key frame and ending just before a subsequence keyframe, is referred to herein as a Group of Pictures (GOP). Key frame 101and predictive frames 103, 105, 107, 109, 111, 113, 115, and 117 areassociated with GOP 133 and maintained in buffer 131 or buffer portion131. An encoding application typically determines the length and frametypes included in a GOP. According to various embodiments, an encoderprovides the sequence of frames to the streaming server. In someexamples, a GOP is 15 frames long and includes an initial key frame suchas an I frame followed by predictive frames such as B and P frames. AGOP may have a variety of lengths. An efficient length for a GOP istypically determined based upon characteristics of the video stream andbandwidth constrains. For example, a low motion scene can benefit from alonger GOP with more predictive frames. Low motion scenes do not need asmany key frames. A high motion scene may benefit from a shorter GOP asmore key frames may be needed to provide a good user experience.

According to various embodiments, GOP 133 is followed by GOP 137maintained in buffer 135 or buffer portion 135. GOP 137 includes keyframe 119 followed by predictive frames 121, 123, 125, 127, 129, 131,133, and 135. In some examples, a buffer used to maintain the sequenceof frames is a first in first out (FIFO) buffer. When new frames arereceived, the oldest frames are removed from the buffer.

When a client 151 connects, the client receives predictive frame 105initially, followed by predictive frames 107, 109, 111, 113, 115, and117. Client 151 receives a total of 7 predictive frames that can not bedecoded properly. In some instances, the 7 predictive frames are simplydropped by a client. Only after 7 predictive frames are received doesclient 151 receive a key frame 119. When a client 153 connects, theclient receives predictive frame 109 initially, followed by predictiveframes 111, 113, 115, and 117. Client 153 receives a total of 5predictive frames that can not be decoded correctly. In some instances,the 5 predictive frames are simply dropped by a client. Only after 5predictive frames are received does client 153 receive a key frame 119.When a client 155 connects, the client receives predictive frame 121initially, followed by predictive frames 123, 125, 127, 129, 131, 133,and 135. Client 155 receives a total of 8 predictive frames that can notbe decoded correctly. In some instances, the 8 predictive frames aresimply dropped by a client. Only after 8 predictive frames are receiveddoes client 155 receive a key frame.

Transmitting predictive frames when a client requests a connection isinefficient and contributes to a poor user experience. Consequently, thetechniques of the present invention contemplate providing a key frameinitially to a client when a client requests a connection.

FIG. 2 is a diagrammatic representation showing another example of asequence of frames. According to various embodiments, a sequence offrames such as a sequence of video frames is received at a streamingserver. In some embodiments, the sequence of video frames is associatedwith a particular channel and a buffer is assigned to each channel.Other sequences of video frames may be held in other buffers assigned toother channels. In other examples, buffers or portions of buffers aremaintained for separate video streams and separate channels. Inparticular embodiments, key frame 201 is received early along time axis241. One example of a key frame 201 is an I frame that includessubstantially all of the data needed for a client device to display aframe of video. Key frame 201 is followed by predictive frames 203, 205,207, 209, 211, 213, 215, and 217.

According to various embodiments, a sequence of different frames types,beginning with a key frame and ending just before a subsequence keyframe, is referred to herein as a Group of Pictures (GOP). Key frame 201and predictive frames 203, 205, 207, 209, 211, 213, 215, and 217 areassociated with GOP 233 and maintained in buffer 231 or buffer portion231. An encoding application typically determines the length and frametypes included in a GOP. According to various embodiments, an encoderprovides the sequence of frames to the streaming server. In someexamples, a GOP is 15 frames long and includes an initial key frame suchas an I frame followed by predictive frames such as B and P frames. AGOP may have a variety of lengths. An efficient length for a GOP istypically determined based upon characteristics of the video stream andbandwidth constrains. For example, a low motion scene can benefit from alonger GOP with more predictive frames. Low motion scenes do not need asmany key frames. A high motion scene may benefit from a shorter GOP asmore key frames may be needed to provide a good user experience.

According to various embodiments, GOP 233 is followed by GOP 237maintained in buffer 235 or buffer portion 235. GOP 237 includes keyframe 219 followed by predictive frames 221, 223, 225, 227, 229, 231,233, and 235. In some examples, a buffer used to maintain the sequenceof frames is a first in first out (FIFO) buffer. When newer frames arereceived, a corresponding number of older frames are removed from thebuffer.

When a client 251 connects, the client receives no longer receives apredictive frame initially. According to various embodiments, the client251 receives the earliest key frame available. In some instances, theearliest key frame still available in the buffer may be key frame 201.The client does not need to drop any frames or display distorted images.Instead the client 251 immediately receives a key frame that includessubstantially all of the information necessary to begin playing thestream. Similarly, when client 253 requests a connection, the clientreceives key frame 201 initially. If key frame 201 is no longeravailable in the buffer, a client connecting would receive key frame219, even if this means that predictive frames 203, 205, 207, 209, 211,213, 215, and 217 are skipped. For example, client 255 may connect at atime that would have provided predictive frame 211, but the streamingserver intelligently identifies the next available key frame as keyframe 219 and provides that key frame 219 to the client 255. Nopredictive frames are inefficiently transmitted at the beginning of aconnection request. According to various embodiments, only key framesare initially provided upon connection requests.

According to various embodiments, a streaming server performs processingon each received frame to determine which frames are key frames.Identifying key frames may involve decoding or partially decoding aframe. In other examples, key frames may be identified based upon thesize of the frame, as key frames are typically much larger thanpredictive frames. In other examples, only a subset of frames aredecoded or partially decoded. In still other examples, once a key frameis determined, the streaming server determines the GOP size N andidentifies each Nth frame following a key frame as a subsequent keyframe. A variety of approaches can be used to determine key frames andpredictive frames. Although the techniques of the present inventioncontemplate efficient mechanisms for identifying key frames, thestreaming server does perform some additional processing.

Furthermore, the streaming server may be providing a predictive frame,such as predictive frame 213, to an already connected client whileproviding a key frame 219 to a new client making a connection request.This can result in a slight but typically unnoticeable time variance inthe media viewed by different clients. That is, a first client may bereceiving predictive frames 213, 215, and 217 while a second client maybe receiving key frame 219 and predictive frames 221 and 223. Thetechniques of the present invention recognize that this time shift isnot disruptive of a typical user experience and a streaming server istypically capable of handling providing different frames from a streamto different client devices.

FIG. 3 is a diagrammatic representation showing one example of a networkthat can use the techniques of the present invention. Although oneparticular example showing particular devices is provided, it should benoted that the techniques of the present invention can be applied to avariety of streaming servers and networks. According to variousembodiments, the techniques of the present invention can be used on anystreaming server having a processor, memory, and the capability ofidentifying characteristics of frames such as frame type in mediastream. According to various embodiments, a streaming server is providedwith video streams from an associated encoder and handles connectionrequests from client devices such as computer systems, mobile phones,personal digital assistants, video receivers, and any other devicehaving the capability of decoding a video stream.

According to various embodiments, media content is provided from anumber of different sources 385. Media content may be provided from filmlibraries, cable companies, movie and television studios, commercial andbusiness users, etc. and maintained at a media aggregation server 361.Any mechanism for obtaining media content from a large number of sourcesin order to provide the media content to mobile devices in livebroadcast streams is referred to herein as a media content aggregationserver. The media content aggregation server 361 may be clusters ofservers located in different data centers. According to variousembodiments, content provided to a media aggregation server 361 isprovided in a variety of different encoding formats with numerous videoand audio codecs. Media content may also be provided via satellite feed357.

An encoder farm 371 is associated with the satellite feed 387 and canalso be associated with media aggregation server 361. The encoder farm371 can be used to process media content from satellite feed 387 as wellas possibly from media aggregation server 361 into potentially numerousencoding formats. The media content may also be encoded to support avariety of data rates. The media content from media aggregation server361 and encoder farm 371 is provided as live media to a streaming server375. According to various embodiments, the encoder farm 371 convertsvideo data into video streams such as MPEG video streams with key framesand predictive frames.

Possible client devices 301 include personal digital assistants (PDAs),cellular phones, personal computing devices, computer systems,television receivers, etc. According to particular embodiments, theclient devices are connected to a cellular network run by a cellularservice provider. Cell towers typically provide service in differentareas. Alternatively, the client device can be connected to a wirelesslocal area network (WLAN) or some other wireless network. Live mediastreams provided over RTSP are carried and/or encapsulated on any one ofa variety of networks.

In particular embodiments, some client devices are also connected over awireless network to a media content delivery server 331. The mediacontent delivery server 331 is configured to allow a client device 301to perform functions associated with accessing live media streams. Forexample, the media content delivery server allows a user to create anaccount, perform session identifier assignment, subscribe to variouschannels, log on, access program guide information, and obtaininformation about media content, etc. According to various embodiments,the media content delivery server does not deliver the actual mediastream, but merely provides mechanisms for performing operationsassociated with accessing media.

In other implementations, it is possible that the media content deliveryserver also provides media clips, files, and streams. The media contentdelivery server is associated with a guide generator 351. The guidegenerator 351 obtains information from disparate sources includingcontent providers 381 and media information sources 383. The guidegenerator 351 provides program guides to database 355 as well as tomedia content delivery server 331 to provide to mobile devices 301. Themedia content delivery server 331 is also associated with an abstractbuy engine 341. The abstract buy engine 341 maintains subscriptioninformation associated with various client devices 301. For example, theabstract buy engine 341 tracks purchases of premium packages.

Although the various devices such as the guide generator 351, database355, media aggregation server 361, etc. are shown as separate entities,it should be appreciated that various devices may be incorporated onto asingle server. Alternatively, each device may be embodied in multipleservers or clusters of servers. According to various embodiments, theguide generator 351, database 355, media aggregation server 361, encoderfarm 371, media content delivery server 331, abstract buy engine 341,and streaming server 375 are included in an entity referred to herein asa media content delivery system.

FIG. 4 is a diagrammatic representation showing one example of astreaming server 421. According to various embodiments, the streamingserver 421 includes a processor 401, memory 403, buffers 431, 433, 435,and 437, and a number of interfaces. In some examples, the interfacesinclude an encoder interface 411, a media aggregation server interface413, and a client device interface 441. The encoder interface 411 andthe media aggregation server interface 413 are operable to receive mediastreams such as video streams. In some examples, hundreds of videostreams associated with hundreds of channels are continuously beingreceived and maintained in buffers 431, 433, 435, and 437 before beingprovided to client devices through client device interface 441.

According to various embodiments, the streaming server 421 handlesnumerous connection requests from various client devices. Connectionrequests can result from a variety of user actions such as a channelchange, an application launch, a program purchase, etc. In someinstances, a streaming server 421 simply provides the first availableframe followed by subsequent frames in response to a client deviceconnection request. However, the techniques of the present inventioncontemplate an intelligent streaming server that identifies key framesin video streams and provides a key frame initially to a client device.The key frame includes substantially all the information needed for aclient device to begin display a correct video frame.

According to various embodiments, buffers 431, 433, 435, and 437 areprovided on a per channel basis. In other examples, buffers are providedon a per GOP basis. Although buffers 431, 433, 435, and 437 are shown asdiscrete entities, it should be recognized that buffers 431, 433, 435,and 437 may be individual physical buffers, portions of buffers, orcombinations of multiple physical buffers. In some examples, virtualbuffers are used and portions of a memory space are assigned toparticular channels based on need.

Although a particular streaming server 421 is described, it should berecognized that a variety of alternative configurations are possible.For example, some modules such as a media aggregation server interfacemay not be needed on every server. Alternatively, the multiple clientdevice interfaces for different types of client devices may be included.A variety of configurations are possible.

FIG. 5 is a flow process diagram showing one example of streaming serverprocessing. At 501, media streams are received. According to variousembodiments, media streams are continuously being received at astreaming server. At 503, media streams are maintained in multiplebuffers. At 505, key frames in media streams are identified. In someexamples, identifying key frames may involve determining the videocodec, the GOP size, and/or the frame size and performing decoding orpartial decoding of frames. A streaming server may be able to determinekey frames by identifying the start of a GOP and the GOP size andflagging each start of a GOP as a key frame. A streaming server may alsoidentify larger frames as key frames.

Partial decoding or full decoding can also be used. At 507, a connectionrequest from a client device is received. At 509, a key frame toinitially provide to the client device is identified. In some examples,the key frame identified is the earliest key frame for the requestedchannel available in a buffer for the channel. At 511, the key frame andsubsequent predictive and key frames are sent to the client device 511.

FIG. 6 is a flow process diagram showing one example of client deviceprocessing. In some examples, a client device is a mobile device.However, it should be noted that a client device can be any deviceassociated with a decoder that is capable of displaying a video frame.That is a client device can be any computer system, portable computingdevice, gaming device, mobile phone, receiver, etc. At 601, a request isreceived for a media stream. According to various embodiments, therequest on the client device may be the result of a user action. At 603,the client device sends a connection request to the streaming server.According to various embodiments, the connection request identifies aparticular program or channel. At 605, a key frame is received from thestreaming server. According to various embodiments, the client devicereceives the key frame first before any other frames. At 607, subsequentpredictive frames and key frames are received from the streaming server.At 609, the client device plays the media stream using the initialreceived key frame. In some examples, the client device includes adecoder that processes the video stream received from the streamingserver. In other examples, a decoding device may reside between theclient device and the streaming server, and the client device simplyplays video data.

While the invention has been particularly shown and described withreference to specific embodiments thereof, it will be understood bythose skilled in the art that changes in the form and details of thedisclosed embodiments may be made without departing from the spirit orscope of the invention. It is therefore intended that the invention beinterpreted to include all variations and equivalents that fall withinthe true spirit and scope of the present invention.

What is claimed is:
 1. A method, comprising: receiving a first mediastream at a client device from a streaming server, the streaming serverreceiving the first media stream as live media from a media aggregationserver, the first media stream being converted by an encoder farm intokey frames and predictive frames; sending a channel change request fromthe client device to the streaming server, the channel change requestcorresponding to a switch from the first media stream to a second mediastream; and receiving a key frame at the client device in response tosending the channel change request, the key frame being identified asthe next available key frame associated with the second media streamafter the streaming server receives the channel change request, whereinreceiving the key frame results in a time variance between receiving thesecond media stream on the client device and receiving the second mediastream on a different client device, wherein the second media stream isthe same media stream being received at the client device and at thedifferent client device, wherein while the client device is receivingthe key frame, the different client device is receiving a predictiveframe from the same second media stream, wherein the key frame isidentified by detecting frames larger than a particular size wherein thekey frame is received from the streaming server, the streaming serverincluding a key frame sensitive buffer, the key frame sensitive bufferbeing a first-in-first-out (FIFO) buffer configured to identify keyframes in the FIFO buffer even if each such key frame is not the firstavailable frame in the FIFO buffer.
 2. The method of claim 1, whereinthe first media stream is a first video stream and the second mediastream is a second video stream.
 3. The method of claim 1, wherein thekey frame is not the first available frame associated with the secondmedia stream in a buffer maintained at the streaming server at the timethe streaming server receives the channel change request.
 4. The methodof claim 1, wherein the key frame is one of a plurality of key frames ina buffer maintained at the streaming server.
 5. The method of claim 1,wherein the key frame is an I-frame.
 6. The method of claim 1, whereinchannel change does not occur until the key frame can be provided to theclient device.
 7. A system, comprising: an interface configured toreceive a first media stream at a client device from a streaming server,the streaming server receiving the first media stream as live media froma media aggregation server, the first media stream being converted by anencoder farm into key frames and predictive frames; and a processorconfigured to send a channel change request from the client device tothe streaming server, the channel change request corresponding to aswitch from the first media stream to a second media stream; wherein theinterface is further configured to receive a key frame at the clientdevice in response to sending the channel change request, the key framebeing identified as the next available key frame associated with thesecond media stream after the streaming server receives the channelchange request, wherein receiving the key frame results in a timevariance between receiving the second media stream on the client deviceand receiving the second media stream on a different client device,wherein the second media stream is the same media stream being receivedat the client device and at the different client device, wherein whilethe client device is receiving the key frame, the different clientdevice is receiving a predictive frame from the same second mediastream, wherein the key frame is identified by detecting frames largerthan a particular size wherein the key frame is received from thestreaming server, the streaming server including a key frame sensitivebuffer, the key frame sensitive buffer being a first-in-first-out (FIFO)buffer configured to identify key frames in the FIFO buffer even if eachsuch key frame is not the first available frame in the FIFO buffer. 8.The system of claim 7, wherein the first media stream is a first videostream and the second media stream is a second video stream.
 9. Thesystem of claim 7, wherein the key frame is not the first availableframe associated with the second media stream in a buffer maintained atthe streaming server at the time the streaming server receives thechannel change request.
 10. The system of claim 7, wherein the key frameis one of a plurality of key frames in a buffer maintained at thestreaming server.
 11. The system of claim 7, wherein the key frame is anI-frame.
 12. The system of claim 7, wherein channel change does notoccur until the key frame can be provided to the client device.
 13. Anon-transitory computer readable medium comprising one or more programs,the one or more programs comprising instructions to cause a processor toexecute a method, the method comprising: receiving a first media streamat a client device from a streaming server, the streaming serverreceiving the first media stream as live media from a media aggregationserver, the first media stream being converted by an encoder farm intokey frames and predictive frames; sending a channel change request fromthe client device to the streaming server, the channel change requestcorresponding to a switch from the first media stream to a second mediastream; and receiving a key frame at the client device in response tosending the channel change request, the key frame being identified asthe next available key frame associated with the second media streamafter the streaming server receives the channel change request, whereinreceiving the key frame results in a time variance between receiving thesecond media stream on the client device and receiving the second mediastream on a different client device, wherein the second media stream isthe same media stream being received at the client device and at thedifferent client device, wherein while the client device is receivingthe key frame, the different client device is receiving a predictiveframe from the same second media stream, wherein the key frame isidentified by detecting frames larger than a particular size wherein thekey frame is received from the streaming server, the streaming serverincluding a key frame sensitive buffer, the key frame sensitive bufferbeing a first-in-first-out (FIFO) buffer configured to identify keyframes in the FIFO buffer even if each such key frame is not the firstavailable frame in the FIFO buffer.
 14. The non-transitory computerreadable medium of claim 13, wherein the first media stream is a firstvideo stream and the second media stream is a second video stream. 15.The non-transitory computer readable medium of claim 13, wherein a mediacontent delivery server provides mechanisms for performing operationsassociated with accessing media.
 16. The non-transitory computerreadable medium of claim 13, wherein the key frame is not the firstavailable frame associated with the second media stream in a buffermaintained at the streaming server at the time the streaming serverreceives the channel change request.
 17. The non-transitory computerreadable medium of claim 13, wherein the key frame is one of a pluralityof key frames in a buffer maintained at the streaming server.
 18. Thenon-transitory computer readable medium of claim 13, wherein the keyframe is an I-frame.